A projection image may be acquired from an electromagnetic wave that penetrates from a source generating the electromagnetic wave through an object, through a detection unit. Also, a tomography image may be reconstituted through a back-projection method for the acquired projection image.
A detector value is calculated from a pixel when performing a projection, but the pixel value is inferred from the detector value when performing a back-projection. A process of estimating the detector value and the pixel value is required in this process.
However, in projection and back-projection processes, a plurality of pixels included in a pixel grid contribute to a plurality of detector cells included in the detector unit, and thus an artifact exists in comparison with an original image.
Therefore, there is a need for projection and back-projection methods that accurately reflect a contribution of each pixel value to a detector value and a contribution of each detector value to a pixel value.